Effect of biosorption of Pb(II), Cu(II) and Cd(II) on the zeta potential and flocculation of Nocardia sp.

This study provides quantitative evidence for the adsorption of metal ions (Pb2+, Cu2+ and Cd2+) on the biomass of Nocardia sp. The adsorption of metal ions to the biomass varies with the type of metal cations and their electro negativity. It suggests that the adsorption of Pb2+. Cu2+ and Cd2+ is mainly due to electrostatic attraction. Microelectrophoretic studies were used in the i.e.p. determination, and effect of the metal ion concentration on the zeta potential of the Nocardia cells was investigated. The electrokinetic data show that the i.e.p. of Nocardia cells is around pH 3.5. An increase of the metal ion concentration causes a decrease in negative value of zeta potential of Nocardia cells. The combination of oppositely charged flocculant and surfactant was used for the separation of Nocardia cells after the ion adsorption. It was found that the combination of cationic surfactant (CTAB) and anionic flocculants (Magnafloc 358) produces very large flocs suitable for separation by settling. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.